A projection display device, such as a projector, projects an image (hereinafter, referred to as a projector image) which is output from, for example, a PC to the projector onto a screen. In this case, when the projector is arranged so as to be inclined with respect to the screen and the optical axis of a lens provided in the projector (hereinafter, referred to as the optical axis of the projector) is not parallel to a normal vector of the plane of the screen, a projection image which is projected onto the screen (hereinafter, referred to as a screen-projected image) is distorted in a trapezoidal shape as viewed from a direction directly facing the screen. In order to comfortably view the screen-projected image, it is necessary to correct the distortion of the screen-projected image.